JP2010068410A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect an edge of a document without degrading image reading performance, in an image reader. <P>SOLUTION: This image reader includes an edge-detecting light source 32 arranged on the downstream side of a holding member 31 in a document transport direction. The edge-detecting light source 32 emits light toward an edge face of a document transported while being interposed between the holding member 31 and platen glass 11. In the image reader, the edge of the document is detected by receiving the light emitted from the edge-detecting light source 32 and reflected on the edge face of the document by a reading sensor 16. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus.

  2. Description of the Related Art An image reading apparatus that reads an image of a document while sequentially conveying the document with an automatic document feeder is known. In this type of image reading apparatus, since it is necessary to detect the edge of the document in order to obtain the reading start timing of the document, a mechanism for detecting the edge of the document (hereinafter referred to as an edge detection mechanism) is generally used. Provided.

For example, Patent Document 1 includes a platen roller provided with a plurality of grooves by deleting a specific width of platen rubber at specific positions in the main scanning direction, and from the light source through each groove of the platen roller, from the document insertion side. Irradiate light toward the reading surface of the contact image sensor, compare the output signal from the position corresponding to the groove portion of the contact image sensor based on the light irradiation from the light source and a specific threshold by the comparison unit, Based on the comparison information of the comparison means, the determination means determines the leading edge of the document.
JP-A-8-307590

By the way, in the image reading apparatus provided with the document feeding device, by providing the end detection mechanism, the end detection mechanism may affect the image reading and may deteriorate the image reading performance. Further, for example, it is conceivable that the edge detection mechanism is arranged away from the reading position of the document so that the edge detection mechanism does not affect the image reading. However, as the edge detection mechanism moves away from the document reading position, the detection accuracy of the document reading start timing decreases.
SUMMARY OF THE INVENTION An object of the present invention is to realize highly accurate document edge detection in an image reading apparatus or the like without impairing image reading performance.

  The invention according to claim 1 is an image reading unit that reads an image of a document to be transported, an irradiation unit that irradiates light from a downstream side in the transport direction of the document toward an end surface of the document, and the document that is transported A light receiving unit that receives light reflected by the end surface of the document, and a tip detection unit that detects the leading end of the document based on the reflected light reflected by the end surface of the document received by the light receiving unit. The image reading apparatus is characterized.

According to a second aspect of the present invention, the irradiating unit irradiates the end surface of the original with light so that a light and dark pattern is formed in the width direction of the original. It is an image reading apparatus of description.
A third aspect of the present invention is the image reading apparatus according to the first or second aspect, wherein the irradiation unit includes a plurality of light sources having different emission colors.
A fourth aspect of the present invention is the image reading apparatus according to any one of the first to third aspects, wherein the image reading unit and the light receiving unit use a single light receiving sensor.

  According to a fifth aspect of the present invention, there is provided a document table on which a document to be transported is placed and which transmits light irradiated to the document surface of the document and reflected light from the document surface, and the document surface of the document to be transported A first light source that irradiates light toward the document table, a pressing unit that presses the document to be conveyed toward the document table, and a side on which the document is placed on the document table. A second light source that emits light between the pressing unit and the document table; a light receiving unit that receives light emitted from the first light source and the second light source; and the light receiving unit An image reading apparatus comprising: a leading edge detecting unit that detects a leading edge of the document based on light emitted from a second light source that receives light.

According to a sixth aspect of the present invention, the second light source is configured such that, when the document is not sandwiched between the pressing unit and the document table, the irradiated light is blocked by the pressing unit. The image reading apparatus according to claim 5, wherein the image reading apparatus is set.
The invention according to claim 7 is characterized in that the second light source has an incident angle with respect to the document table so that light directly incident on the document table does not travel toward the light receiving unit. An image reading apparatus according to claim 5 or 6.

According to the first aspect of the present invention, compared with the case where the present configuration is not provided, it is possible to suppress the deterioration of the image reading performance and to detect the edge portion of the document with higher accuracy.
According to the second aspect of the invention, it is possible to realize end detection with reduced false detection by recognizing the pattern of light irradiation in the irradiation section.
According to the third aspect of the present invention, it is possible to realize end detection with reduced false detection by recognizing the pattern of the luminescent color in the irradiation section.
According to the fourth aspect of the present invention, it is possible to further reduce the deviation between the reading position of the document and the detection position of the end portion of the document, as compared with the case where this configuration is not provided.

According to the fifth aspect of the present invention, compared to the case where the present configuration is not provided, it is possible to suppress the deterioration of the image reading performance and realize the document edge detection with higher accuracy.
According to invention of Claim 6, the period when the light irradiated from a 2nd light source injects into a light-receiving part can be shortened.
According to the seventh aspect of the present invention, it is possible to limit the incidence of the light emitted from the second light source to the light receiving unit.

<Embodiment 1>
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating an overall configuration of the image reading apparatus 1.
The image reading apparatus 1 includes a scanner device 10 that reads an image by scanning the document P, and a document feeding device 20 that sequentially conveys the document P from a stacked document bundle.

The scanner device 10 reads a platen glass 11 on which a document P to be read is placed, a document P placed on the platen glass 11 in a stationary state, or a document P conveyed on the platen glass 11 by the document feeder 20. And a reading unit 12 for performing.
The reading unit 12 is imaged by a reading light source 13 that irradiates light toward the original P, an equal-magnification lens array 15 that focuses the light reflected by the original P on the reading sensor 16, and an equal-magnification lens array 15. And a reading sensor 16 that photoelectrically converts the optical image. As described above, the reading unit 12 according to the present embodiment reads an image with the equal magnification optical system.

  The reading light source 13 as an example of the first light source emits light toward the document P when reading the image of the document P. Further, the reading light source 13 of the present embodiment emits white light. The reflection plate 14 reflects light that does not travel directly toward the original P out of the light emitted from the reading light source 13 to the original P. In the reading unit 12 of the present embodiment, by providing the reflecting plate 14, the document P is efficiently irradiated with light.

  A reading sensor 16 (light receiving sensor) as an example of an image reading unit includes a substrate and a plurality of pixel columns mounted on the substrate. The reading sensor 16 of the present embodiment has a red (R) pixel column, a green (G) pixel column, and a blue (B) pixel column. Color filters for transmitting different wavelength components are attached to the red pixel row, the green pixel row, and the blue pixel row, respectively. Thus, the reading sensor 16 functions as a color sensor for the red pixel column, the green pixel column, and the blue pixel column. As the reading sensor 16, a CCD, a CMOS (Complementary Metal Oxide Semiconductor) sensor, a contact sensor, or the like can be used.

  The reading sensor 16 functioning as a light receiving unit receives the light emitted from the reading light source 13 and reflected by the original P when reading the image, and reads the image of the original P. In addition, the reading sensor 16 receives light emitted from the edge detection light source 32 and reflected by the leading edge of the document P when detecting the edge of the document P, which will be described later. Then, the reading sensor 16 sends the received light data received in each pixel column to the control unit 40.

By the way, in order to detect the edge portion of the document P, for example, a sensor separate from the reading sensor 16 may be provided to configure the edge detection mechanism of the document P. However, in this case, an edge detection sensor must be arranged at a position different from the reading sensor 16. Therefore, the detection position of the leading end of the document P is separated from the image reading position, which leads to a decrease in detection accuracy of the reading start timing of the document P.
On the other hand, in the image reading apparatus 1 of the present embodiment, a single reading sensor 16 is used in combination for image reading of the document P and edge detection of the document P. Thereby, in the image reading apparatus 1, the detection accuracy of the reading start timing of the document P is improved by matching the image reading position with the leading edge detection position of the document P. Further, in the image reading apparatus 1, the apparatus configuration is simplified by using the reading sensor 16 in combination with the image reading of the document P and the edge detection of the document P.

  The scanner device 10 includes a control unit 40 that functions as a tip detection unit. The control unit 40 controls the reading operation of each member in the scanner device 10, performs image processing of the read image data, and controls the document conveying operation in the document feeding device 20. Further, the control unit 40 also detects an end portion of the document P described later. The above functions in the control unit 40 are realized by a CPU or the like controlled by a program.

  The document feeder 20 includes a document stacking unit 21 that stacks a bundle of documents composed of a plurality of documents P, and a discharge stacking unit 22 that is provided below the document stacking unit 21 and stacks the document P that has been read. Further, the document feeder 20 is provided with a feeding roll 23 for feeding the documents P stacked on the document stacking unit 21 and a separating unit 24 for separating sheets one by one. Further, in the transport path 25 for transporting the original P, a pre-registration roll 26 that transports the original P, which has been wound one by one, toward the downstream roll, and an image reading position while performing registration adjustment on the original P. And a registration roll 27 for supplying the original P toward the head.

The document feeder 20 includes a transport roll 28 that transports the document P being read by the scanner device 10 and an out-roll 29 that transports the document P read by the scanner device 10 further downstream. The document feeder 20 includes a discharge roll 30 that discharges the document P after image reading to the sheet discharge stacking unit 22.
Further, the document feeder 20 includes a pressing member 31 disposed between the registration roll 27 and the conveyance roll 28 and an end detection light source 32 provided on the downstream side of the pressing member 31 in the conveyance direction of the document P. Yes.

FIG. 2 is a diagram for explaining in detail the members around the image reading position. 2A is a side view seen from the same direction as the image reading apparatus 1 shown in FIG. FIG. 2B is a view of the pressing member 31, the edge detection light source 32, and the like as viewed from the direction of the arrow A shown in FIG.
As shown in the example of FIG. 2A, the pressing member 31 is provided to face the reading sensor 16 in the reading unit 12 when reading an image while conveying the document P. Further, as shown in the example of FIG. 2B, the pressing member 31 is a rectangular member provided over the entire width of the document P in the width direction (main scanning direction). And the pressing member 31 of this embodiment is comprised with the white member. Further, the pressing member 31 is configured not to transmit light from an end detection light source 32 described later. The pressing member 31 having such characteristics is pressed toward the platen glass 11 by an unillustrated elastic member or the like.

  When the document P is conveyed toward the image reading position SP, the pressing member 31 sandwiches the document P with the platen glass 11 and presses the document P toward the platen glass 11. As described above, in the image reading apparatus 1 of the present embodiment, the pressing member 31 is provided to suppress the generation of wrinkles or the like that may occur on the document P during image reading, or the focal length of the equal-magnification lens array 15 in image reading. And the position of the original P are stabilized.

  The pressing member 31 has a function as a background plate when reading an image while conveying the original P. In this embodiment, the color of the pressing member 31 is configured to be white so that the color of the pressing member 31 is prevented from being reflected in the document P to be read. Further, by setting the color of the pressing member 31 to white, for example, when reading a document P having punch holes, the punch holes on the read image can be erased. In addition, as the pressing member 31, the surface facing the platen glass 11 may be white coated or a white sheet may be formed.

  The edge detection light source 32 as an example of the irradiation unit and the second light source is a light source used to detect the arrival of the leading end of the conveyed document P at the image reading position SP. For example, a light emitting diode (LED) can be used as the light source 32 for edge detection in the present embodiment. In addition, the edge detection light source 32 of the present embodiment includes two light emitting diodes 32W that emit light, as shown in the example of FIG. The edge detection light source 32 emits light from two places in the width direction of the document P toward the leading end of the document P being conveyed. In the end detection light source 32 of the present embodiment, the directivity of the emitted light is enhanced by combining a light emitting diode and a lens.

  Further, as shown in FIG. 2A, the edge detection light source 32 of the present embodiment is provided on the downstream side of the pressing member 31 in the conveyance direction of the document P. The edge detection light source 32 emits light toward the leading edge of the document P being conveyed while being sandwiched between the pressing member 31 and the platen glass 11. In the image reading apparatus 1 according to the present embodiment, the light emitted from the edge detection light source 32 and reflected by the edge surface of the document P is received by the reading sensor 16 to detect the edge of the document P.

Here, in order to detect the leading end portion of the document P, it is conceivable that a light source is provided so as to face the reading sensor 16 and light is emitted in the direction of arrow A shown in FIG.
In this case, the reading sensor 16 receives light from the light source until the document P reaches. When the document P arrives, the light emitted from the light source is blocked by the document P and is not received by the reading sensor 16. In this case, the leading edge of the document P is detected by looking at the change in the intensity of light received from the light source in the reading sensor 16.
However, in the image reading apparatus 1, it is generally required to provide the pressing member 31. In the above configuration, if the pressing member 31 is provided, for example, a notch or the like is provided in the pressing member 31, and light is irradiated from the gap toward the leading end side of the document. Then, a notch or the like provided in the pressing member 31 is reflected in the document P to be read, and in some cases, for example, a streak-like disorder may occur in the read image.

  In contrast, the edge detection light source 32 of the present embodiment makes light incident between the pressing member 31 and the platen glass 11 from the downstream side in the transport direction of the document P. Accordingly, it is not necessary to provide a notch or the like in the pressing member 31 in order to pass the light emitted from the end detection light source 32. As a result, in the image reading apparatus 1 of the present embodiment, the pressing member 31 is suppressed from appearing on the document P to be read, and the deterioration of the image reading performance is prevented.

Further, in the document feeder 20 to which the present embodiment is applied, as a result of arranging the light source downstream, as shown in FIG. 2A, a conveyance roll is provided between the end detection light source 32 and the pressing member 31. 28 is located.
When the transport roll 28 is arranged in this way, the light emitted from the edge detection light source 32 is blocked by the transport roll 28. On the other hand, the conveyance roll 28 of this embodiment is provided with the three roll members 28a, 28b, and 28c arranged in the axial direction, as shown in FIG.2 (b). And in the conveyance roll 28, the clearance gap is provided between the adjacent roll members like the roll member 28a and the roll member 28b, for example. The edge detection light source 32 irradiates light toward the image reading position SP through the gap in the transport roll 28.

Next, the irradiation angle of the irradiation light Bm from the edge detection light source 32 will be described.
In the present embodiment, the edge detection light source 32 emits light toward the leading edge of the document P conveyed to the image reading position SP. In the present embodiment, the reading sensor 16 receives the light irregularly reflected at the leading end of the document P, thereby determining that the leading end of the document P has reached the image reading position SP. Accordingly, the irradiation light Bm from the edge detection light source 32 is set so as not to travel to the reading sensor 16 (equal magnification lens array 15) except for the timing of reflection at the leading edge of the document P.

FIG. 3 is a diagram for explaining the incident angle θ of the irradiation light Bm from the edge detection light source 32 with respect to the platen glass 11. FIG. 3A is a diagram illustrating an example of a path of light incident on the platen glass 11 from the edge detection light source 32. FIG. 3B is a diagram illustrating the relationship between the incident angle θ of the light irradiated from the edge detection light source 32 to the platen glass 11 and the transmittance of the platen glass 11.
The irradiation light Bm from the edge detection light source 32 of the present embodiment is set so that the incident angle θ with respect to the surface of the platen glass 11 is 60 degrees or more. Then, as shown in FIG. 3A, the light directly incident on the platen glass 11 from the edge detection light source 32 travels in a direction away from the 1 × lens array 15. The light that is directly incident on the platen glass 11 from the edge detection light source 32 is configured to travel outside the field angle range of the equal-magnification lens array 15.

  Further, as shown in FIG. 3B, the transmittance of light incident on the platen glass 11 tends to decrease as the incident angle θ of light with respect to the platen glass 11 increases. In the present embodiment, based on this relationship, the incident angle θ of the irradiation light Bm from the edge detection light source 32 to the platen glass 11 is set to be 60 degrees or more.

Next, an image reading operation in the image reading apparatus 1 will be described.
First, the case where the image reading apparatus 1 reads an image by placing the document P on the platen glass 11 will be described. When the document P is set on the platen glass 11 and reading is started, the reading unit 12 starts to move in the scanning direction (for example, the direction of arrow X in FIG. 1). At this time, light is emitted toward the original P from the reading light source 13 in the reading unit 12. Then, the reflected light reflected by the original P is imaged on the reading sensor 16 by the equal-magnification lens array 15. The reading sensor 16 photoelectrically converts the formed optical image and sends the received light data to the control unit 40.

Next, a case where the image reading apparatus 1 reads an image of the original P while conveying the original P by the original feeding apparatus 20 will be described.
When a document P is set on the document stacking unit 21 and an instruction to start reading is received, the reading unit 12 stands by in a state where it is stopped at the position indicated by the solid line shown in FIG. Further, the reading light source 13 and the edge detection light source 32 are turned on. Thereafter, the document P is supplied to the document reading position by the document feeder 20. When the timing at which the leading edge of the document P reaches the image reading position SP is detected based on the irradiation light Bm from the edge detection light source 32, image reading of the document P is started. The light emitted from the reading light source 13 toward the original P is reflected by the original P, and forms an image on the reading sensor 16 by the equal-magnification lens array 15. The reading sensor 16 photoelectrically converts the formed optical image and sends the image data to the control unit 40. Such scanning is performed in the sub-scanning direction of the document P, and the document reading for one document P is completed.

FIG. 4 is a diagram for explaining an example of the operation of detecting the leading edge of the document P.
As shown in the example of FIG. 4A, when light from the edge detection light source 32 is irradiated in a state where the document P has not reached the position where the pressing member 31 is provided, the irradiation light Bm is It is blocked by the pressing member 31 and does not proceed to the reading sensor 16. At this time, as described above, the reading light source 13 is turned on. Accordingly, the light received by the reading sensor 16 (equal magnification lens array 15) is light emitted from the reading light source 13 and reflected by the pressing member 31.

Next, as shown in the example of FIG. 4B, when the document P reaches the position where the pressing member 31 is provided and is sandwiched between the pressing member 31 and the platen glass 11, the pressing member 31 is It lifts away from the platen glass 11. A gap corresponding to the thickness of the document P is formed between the pressing member 31 and the platen glass 11. Then, the light emitted from the end detection light source 32 enters between the platen glass 11 and the pressing member 31.
Here, as described with reference to FIG. 3, the incident angle θ with respect to the platen glass 11 of the irradiation light Bm from the edge detection light source 32 is determined in advance. Therefore, the light emitted from the edge detection light source 32 enters the platen glass 11 and then exits outside the range of the angle of view of the equal-magnification lens array 15 unless it strikes the leading edge of the document P. . Therefore, the light emitted from the edge detection light source 32 does not travel to the reading sensor 16 side. Accordingly, even in this state, similarly to the state shown in FIG. 4A, the light received by the reading sensor 16 is light that is emitted from the reading light source 13 and reflected by the pressing member 31.

  Then, as shown in the example of FIG. 4C, the document P is further conveyed, and the leading end of the document P reaches a position where it receives light emitted from the edge detection light source 32. Then, the light irradiated from the edge detection light source 32 is irradiated onto a surface (hereinafter referred to as an end surface) formed by the thickness direction and the width direction of the document P. The irradiation light Bm from the edge detection light source 32 is irregularly reflected on the end surface of the document P. Of the light irregularly reflected on the end surface of the document P, components included in the field angle range of the equal-magnification lens array 15 are condensed by the equal-magnification lens array 15. Further, the light is guided to the reading sensor 16 by the equal-magnification lens array 15. At this time, the light emitted from the light source 13 for reading and reflected by the pressing member 31 is also guided to the reading sensor 16. Accordingly, the light received by the reading sensor 16 in this state is both the light emitted from the reading light source 13 and reflected by the holding member 13 and the light emitted from the edge detection light source 32 and reflected from the end face of the document P. Of light.

  The image reading apparatus 1 according to the present embodiment detects the leading edge of the document P by looking at the change in received light intensity at the reading sensor 16. That is, in the state shown in the examples of FIGS. 4A and 4B, the amount of light received by the reading sensor 16 is light from the reading light source 13. On the other hand, as shown in the example of FIG. 4C, when the leading end of the document P reaches the image reading position SP, the amount of light received by the reading sensor 16 is the light from the light source 13 for reading and the end. It becomes both light from the light from the light source 32 for part detection. Therefore, by detecting the timing when the received light intensity at the reading sensor 16 becomes high, it is determined that the timing is the timing when the leading edge of the document P reaches the reading position SP.

As shown in the example of FIG. 4D, when the document P is further transported, the light from the edge detection light source 32 is blocked by the transported document P. When the leading edge of the document P passes the document reading position, the light from the edge detection light source 32 does not travel to the reading sensor 16. Accordingly, the light received by the reading sensor 16 in this state is the light emitted from the reading light source 13 and reflected by the holding member 13.
As described above, the light emitted from the edge detection light source 32 enters the reading sensor 16 at the timing when the leading end of the document P reaches the document reading position SP. Conversely, when the leading edge of the document P is not located at the document reading position SP, the light from the edge detection light source 32 does not enter the reading sensor 16. Therefore, after the edge of the document P is detected, the influence of the irradiation light Bm from the edge detection light source 32 on the image reading is suppressed.

  In order to increase the accuracy of edge detection, the amount of reflected light from the end surface of the document P is further increased, and the received light intensity of the reflected light from the end surface of the document P received by the reading sensor 16 is increased. Conceivable. Therefore, for example, the light amount of the irradiation light Bm of the edge detection light source 32 may be made larger than that of the reading light source 13. In the image reading apparatus 1 of the present embodiment, as described above, the period during which the irradiation light Bm from the edge detection light source 32 enters the reading sensor 16 is reduced. Further, the irradiation light Bm of the edge detection light source 32 is prevented from directly entering the reading sensor 16. As described above, in the image reading apparatus 1 of the present embodiment, the load on the reading sensor 16 caused by the edge detection light source 32 is reduced, and therefore the irradiation light Bm of the edge detection light source 32 is increased. Is possible.

<Embodiment 2>
FIG. 5 is a diagram for explaining the image reading apparatus 1 according to the second embodiment. FIG. 5A is a diagram illustrating the edge detection light source 32 to which the second exemplary embodiment is applied. FIG. 5B shows a distribution of received light intensity in the width direction of the document P obtained by the reading sensor 16 at the timing when the document P reaches the image reading position.
The image reading apparatus 1 according to the second embodiment is different from the first embodiment in the emission color of the edge detection light source 32. In the second embodiment, the same members and the like as those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
As shown in the example of FIG. 5A, the edge detection light source 32 of the second embodiment includes four blue light emitting diodes 32B that emit blue light. These four blue light emitting diodes 32B are arranged at a predetermined interval in the width direction. The edge detection light source 32 according to the second embodiment emits blue light toward the edge of the document P by the four blue light emitting diodes 32B.

Next, the edge detection operation of the document P in the second embodiment will be described. Here, an example in which the background color of the document P to be read is white will be described.
The leading edge of the document P reaches a position where it receives light emitted from the edge detection light source 32 (see FIG. 4C). Then, the blue light emitted from the edge detection light source 32 is applied to the end surface of the document P. The irradiation light Bm from the edge detection light source 32 is irregularly reflected on the end surface of the document P. Of the blue light irregularly reflected by the end surface of the original P, the blue light reflected at an angle included within the range of the field angle of the equal magnification lens array 15 is condensed by the equal magnification lens array 15. Further, the blue light is guided to the reading sensor 16 by the equal-magnification lens array 15.

At this time, the light emitted from the reading light source 13 and reflected by the pressing member 31 is guided to the reading sensor 16. Therefore, regarding the light emitted from the reading light source 13, any of the red pixel column, the blue pixel column, and the green pixel column in the reading sensor 16 receives light. On the other hand, the light emitted from the edge detection light source 32 and reflected from the leading edge of the document P is blue light. Therefore, the light emitted from the edge detection light source 32 is received by the blue pixel row of the reading sensor 16.
Therefore, as shown in FIG. 5B, in the reading sensor 16, the received light intensity of blue light (blue pixel column) is red light (red pixel column) and green light (green pixel column). It becomes relatively large compared. In the image reading apparatus 1 according to the second embodiment, the arrival timing of the leading edge of the document P is detected based on the timing at which the light receiving intensity of blue light in the reading sensor 16 becomes higher than that of other colors. Yes.

  Usually, when the document P does not reach the pressing member 31, it is considered that the probability that the light receiving intensity of only the blue light is high in the reading sensor 16 is low. Therefore, the image reading apparatus 1 according to the second embodiment can detect the edge of the document P satisfactorily by detecting the timing when the received light intensity of blue light is higher than that of other colors.

  Further, as described above, the edge detection light source 32 includes a plurality of light sources (in this example, four blue light emitting diodes 32B). At the edge of the document P, the amount of light in the areas facing each light source is large, and the areas not facing are small. By configuring the edge detection light source 32 in this way, a light and dark pattern is formed on the light irradiated to the edge of the document P. In the image reading apparatus 1 according to the second embodiment, the edge detection of the document P is performed based on the light irradiation patterns of the four blue light emitting diodes 32 </ b> B in the edge detection light source 32.

Specifically, the arrangement pattern in the width direction of the blue light emitting diode 32B is compared with the distribution in the width direction of the blue light transmitted from the reading sensor 16. For example, as shown in the example of FIG. 5B, comparing the position where the four peaks appear in the distribution of the received light intensity of blue light and the arrangement of the blue light emitting diodes 32B in the edge detection light source 32 are given. It is done. Alternatively, the interval between the four peaks in the distribution of received light intensity of blue light may be compared with the arrangement interval of the blue light emitting diodes 32B in the edge detection light source 32.
As described above, in the image reading apparatus 1 according to the present embodiment, the detection of the edge portion of the document P is not only made based on the magnitude of the received light intensity in the reading sensor 16 but also the distribution (pattern) ).
In the above example, the example in which blue light is used as the emission color of the edge detection light source 32 has been described, but red light or green light may be used.

<Embodiment 3>
FIG. 6 is a diagram for explaining the image reading apparatus 1 according to the third embodiment. FIG. 6A is a diagram illustrating the edge detection light source 32 to which the third embodiment is applied. FIG. 6B shows the distribution of received light intensity obtained by the reading sensor 16 at the timing when the document P reaches the image reading position.
The image reading apparatus 1 according to the third embodiment is different from the first embodiment in the emission color of the edge detection light source 32. In the third embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The edge detection light source 32 of the third embodiment includes two blue light emitting diodes 32B and two red light emitting diodes 32R, as shown in FIG. In the example shown in FIG. 6A, the red light emitting diode 32R, the blue light emitting diode 32B, the red light emitting diode 32R, and the blue light emitting diode 32B are arranged at predetermined intervals in the width direction in this order from the front side of the drawing. Yes. Then, as shown in the example of FIG. 6A, the edge detection light source 32 emits blue light and red light toward the edge of the document P by the blue light emitting diode 32B and the red light emitting diode 32R. .

Next, the edge detection operation of the document P in the third embodiment will be described. Note that the basic operation of edge detection in the third embodiment is the same as that in the first embodiment.
When the document P reaches the image reading position, as shown in FIG. 6B, the received light intensity obtained by the reading sensor 16 is relatively higher for blue light and red light than for green light. Therefore, in the third embodiment, the edge detection of the document P is detected based on the timing at which the blue light and the red light become higher than the green light by looking at the change in the received light intensity in each pixel column of the reading sensor 16. .
Furthermore, in the image reading apparatus 1 according to the third embodiment, the blue light emitting diodes 32B and the red light emitting diodes 32R are alternately arranged. Accordingly, with respect to the distribution of the received light intensity in the reading sensor 16, the blue light peak and the red light peak appear alternately along the width direction of the document P. Then, as described in the second embodiment, for example, edge detection of the document P is determined in correspondence with the arrangement pattern of the blue light emitting diodes 32B and the red light emitting diodes 32R in the edge detection light source 32.

Further, by providing the edge detection light source 32 with a plurality of color light sources as in the third embodiment, it is possible to easily detect the edge of the document P even when the ground color of the document P is not white. For example, when the background color of the conveyed document P is blue, the light emitted from the red light emitting diode 32R among the light emitted from the edge detection light source 32 is absorbed by the document P. In such a case, the edge detection of the document P is performed based on the blue light emitted from the edge detection light source 32.
In the third embodiment, the example in which the edge detection light source 32 emits blue light and red light has been described. However, the embodiment is not limited to the combination of these colors. Any two colors of red light, green light, and blue light may be combined. Further, the edge detection light source 32 may be configured by including three light sources that emit red light, green light, and blue light.

  In the above-described embodiment, a plate-like member is used as the pressing member. However, the present invention is not limited to this. Instead of the pressing member 31 of the present embodiment, a roll member may be used as the pressing portion. In this case, when the document P is conveyed to the image reading position, the roll member as the pressing portion moves in a direction away from the platen glass 11. At this time, the edge detection light source 32 irradiates the leading edge of the document P with light. Then, as described above, the edge detection of the document P is performed, and the image reading start timing of the document P is detected.

1 is a diagram illustrating an overall configuration of an image reading apparatus. It is a figure for demonstrating in detail the member around an image reading position. It is a figure for demonstrating the incident angle with respect to the platen glass of the irradiation light from the edge part light source. FIG. 6 is a diagram for explaining an operation for detecting the leading edge of a document. FIG. 5 is a diagram for explaining an image reading apparatus according to a second embodiment. FIG. 6 is a diagram for explaining an image reading apparatus according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image reading apparatus, 10 ... Scanner apparatus, 12 ... Reading unit, 13 ... Reading light source, 15 ... Same size lens array, 16 ... Reading sensor, 20 ... Document feeder, 32 ... Light source for edge detection, 40 ... Control unit

Claims (7)

An image reading unit for reading an image of a conveyed document;
An irradiation unit configured to irradiate light from the downstream side in the conveyance direction of the document toward the end surface of the document;
A light receiving unit that receives light reflected by the end face of the document being conveyed;
An image reading apparatus comprising: a leading edge detection unit that detects a leading edge of the document based on reflected light reflected by an end surface of the document received by the light receiving unit.   The image reading apparatus according to claim 1, wherein the irradiating unit irradiates the end surface of the document with light so that a light and dark pattern is formed in a width direction of the document.   The image reading apparatus according to claim 1, wherein the irradiation unit includes a plurality of light sources having different emission colors.   The image reading apparatus according to claim 1, wherein the image reading unit and the light receiving unit use a single light receiving sensor. A document table on which a document to be transported is placed and which transmits the irradiation light to the document surface of the document and the reflected light from the document surface;
A first light source that emits light toward the original surface of the original document being conveyed;
A pressing portion for pressing the conveyed document toward the document table;
A second light source that is provided on a side of the document table on which the document is placed and irradiates light between the pressing unit and the document table from the downstream side in the conveyance direction of the document;
A light receiving unit that receives light emitted from the first light source and the second light source;
An image reading apparatus comprising: a leading edge detecting section that detects a leading edge of the document based on light emitted from a second light source received by the light receiving section.   The second light source is set so that irradiated light is blocked by the pressing portion when the document is not sandwiched between the pressing portion and the document table. Item 6. The image reading device according to Item 5.   The incident angle with respect to the document table is set so that the light directly incident on the document table does not travel toward the light receiving unit. Image reading device.

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